1. Field of the Invention
The present invention relates generally to an engine mounting arrangement which employs one or more ERF (electrorheological fluid) filled bushes and more specifically to such an arrangement which features improved control of the voltage which is applied to the electrodes via which the viscosity of the ERF is controlled.
2. Description of the Prior Art
JP-A-60-194828 discloses an engine mount of the arrangement wherein the mounts which are disposed between the engine and the chassis include, in addition to the elastomeric members which provide resilient support, two chambers which are fluidly communicated via an orifice passage or passages. The chambers are filled with an ERF and electrodes are disposed in the orifice passage(s) in a manner which enables a voltage to be impressed across the fluid which is passing through the orifice passage and thus induce a notable change in the viscosity of the same.
In this arrangement the voltage application is controlled in accordance with a parameter such as the engine rotational speed, and in a manner which is intended to enable the selective control of the dynamic spring constant and loss factor of the mount in a number of different vibration frequency ranges.
However, as shown in FIG. 7 the relationship between the applied voltage and the peak floor vibration level is such that the no consideration has been given to the effect of the rate at which the variable viscosity ERF which flows through the orifice passage(s) and the applied voltage has been set at a fixed level.
The optimal voltage which produces the maximum attenuation for the peak floor vibration level is shown in FIG. 7 by the large black dots. By way of example, when engine shake occurs and the maximum voltage is applied to the electrodes, while the flow rate is high there is no problem, however as shown, when the flow rate is low, the attenuation of the peak floor vibration level attenuation is deteriorated. In addition, the application of the high voltage consumes a relatively large amount of energy and reduces the longevity of a number of components which make up the device.